LED Chip Serrated Sidewalls for Thick-Wafer Stealth Dicing
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Solution Overview
Problem
Current stealth dicing methods for cutting thick wafers into LED chips often result in poor yield and reduced luminous brightness due to oblique fractures and electrical failure rates, especially when the laser beam is proximate to the semiconductor light-emitting stack.
Innovation Solution
The method involves forming a light-emitting diode chip with a substrate having a serrated side surface, created by stealth dicing with laser inscribed features spaced apart along the thickness direction of the substrate, which reduces oblique fractures and enhances light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If stealth dicing is performed with higher laser energy to ensure complete splitting of thick wafers, then the splitting yield improves, but the electrical failure rate of LED chips increases due to proximity to the semiconductor light-emitting stack
Solution Approach 1:
The patent divides the single stealth dicing process into multiple sequential dicing operations at different depths. The first dicing forms an initial inscribed mark at a first depth, and the second dicing forms a subsequent inscribed mark at a second depth greater than half the wafer thickness. This segmentation allows complete splitting of thick wafers while using lower laser energy at each stage, avoiding damage to the light-emitting stack and reducing electrical failure rate.
2Illumination intensity
If the dicing street width is increased to reduce damage to light-emitting areas during wafer splitting, then the luminous brightness improves, but the production yield of LED chips decreases
Solution Approach 1:
The patent performs preliminary stealth dicing to form inscribed marks within the wafer before the final splitting operation. These pre-formed inscribed marks guide the splitting process to occur precisely along the desired paths, minimizing oblique fractures and damage to light-emitting areas. This allows the use of narrower dicing streets without compromising luminous brightness, thereby maintaining higher production yield.
3Illumination intensity
If stealth dicing is performed at a depth greater than half the wafer thickness to avoid oblique fractures, then the luminous brightness improves, but the laser beam position becomes proximate to the semiconductor light-emitting stack increasing electrical failure rate
Solution Approach 1:
The patent segments the dicing depth into multiple stages. The first stealth dicing operates at a first depth that is safe from the light-emitting stack, and the second stealth dicing operates at a second depth greater than half the wafer thickness to prevent oblique fractures. This multi-stage approach achieves both goals: sufficient depth to prevent oblique fractures while maintaining safe distance from the light-emitting stack through sequential operations.
4Reliability
If proper laser energy and focal position are used to ensure good optoelectrical property and high yield, then the LED chip quality improves, but the side surface becomes smooth which is not conducive for light emitting
Solution Approach 1:
The patent creates different surface qualities at different locations. The main cutting surfaces remain smooth for good optoelectrical properties, while the side surfaces develop micro-roughness from the multi-stage stealth dicing process. This local differentiation allows the side surfaces to act as light extraction surfaces with enhanced light emission, while the primary cutting faces maintain smooth surfaces for optimal electrical and optical performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the yield and luminous efficiency of LED chips by minimizing oblique fractures and electrical failures, while allowing for complete cutting of thick wafers with reduced dicing street width.
Implementation Method 1
forming a plurality of laser inscribed features by stealth dicing in a portion of a substrate of a light-emitting structure corresponding to a dicing street of the light-emitting structure
Data Source
AI summary
A light-emitting diode chip includes a substrate. The substrate has a side surface configured as a serrated surface, which includes a plurality of laser inscribed features disposed along a thickness direction of the substrate and spaced apart from each other. A method for manufacturing the light-emitting diode chip is also disclosed herein.